Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$119.63	10.205%	$131.8382	$131.84	$131.85	$131.80
Purchase #2	$241.97	11.714%	$270.3144	$270.31	$270.30	$270.30
Purchase #3	$89.65	7.221%	$96.1236	$96.12	$96.10	$96.10
Purchase #4	$60.81	10.330%	$67.0917	$67.09	$67.10	$67.10
Purchase #5	$225.27	13.804%	$256.3663	$256.37	$256.35	$256.40
Purchase #6	$249.66	3.681%	$258.85	$258.85	$258.85	$258.90
Purchase #7	$214.32	4.294%	$223.5229	$223.52	$223.50	$223.50
7 purchase totals =	$1,201.31		$1,304.1071	$1,304.10	$1,304.05	$1,304.10